1 /* 2 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.util.function; 26 27 /** 28 * Apply a function to the input object yielding an appropriate {@code double} 29 * value; this is the {@code double}-bearing specialization for {@link Function}. 30 * 31 * <p>When used as a {@code Function} the default {@code apply} implementation 32 * provided by this interface neither accepts null parameters nor does it return 33 * null results. 34 * 35 * @param <T> the type of input objects to the function 36 * 37 * @since 1.8 38 */ 39 public interface DoubleFunction<T> extends Function<T,Double> { 40 41 /** 42 * {@inheritDoc} 43 * 44 * @param t {@inheritDoc}, must be non-null 45 * @return {@inheritDoc}, always non-null 46 */ 47 @Override 48 public default Double apply(T t) { 49 return applyAsDouble(t); 50 } 51 52 /** 53 * Apply a function to the input object yielding an appropriate 54 * {@code double} value. 55 * 56 * @param t the input object 57 * @return the function result value 58 */ 59 public double applyAsDouble(T t); 60 }